Photoresist compositions are used in microlithography processes for making miniaturized electronic components such as in the fabrication of computer chips and integrated circuits. Generally, in these processes, a thin coating of film of a photoresist composition is first applied to a substrate material, such as silicon wafers used for making integrated circuits. The coated substrate is then baked to evaporate any solvent in the photoresist composition and to fix the coating onto the substrate. The baked coated surface of the substrate is next subjected to an image-wise exposure to radiation.
This radiation exposure causes a chemical transformation in the exposed areas of the coated surface. Visible light, ultraviolet (UV) light, electron beam and X-ray radiant energy are radiation types commonly used today in microlithographic processes. After this image-wise exposure, the coated substrate is treated with a developer solution to dissolve and remove either the radiation-exposed or the unexposed areas of the photoresist.
The trend towards the miniaturization of semiconductor devices has led to the use of new photoresists that are sensitive to lower and lower wavelengths of radiation and has also led to the use of sophisticated multilevel systems to overcome difficulties associated with such miniaturization.
Absorbing antireflective coatings in photolithography are used to diminish problems that result from back reflection of light from highly reflective substrates. Two major disadvantages of back reflectivity are thin film interference effects and reflective notching. Thin film interference, or standing waves, result in changes in critical line width dimensions caused by variations in the total light intensity in the photoresist film as the thickness of the photoresist changes or interference of reflected and incident exposure radiation can cause standing wave effects that distort the uniformity of the radiation through the thickness. Reflective notching becomes severe as the photoresist is patterned over reflective substrates containing topographical features, which scatter light through the photoresist film, leading to line width variations, and in the extreme case, forming regions with complete photoresist loss. An antireflective coating coated beneath a photoresist and above a reflective substrate provides significant improvement in lithographic performance of the photoresist. Typically, the bottom antireflective coating is applied on the substrate and then a layer of photoresist is applied on top of the antireflective coating. The antireflective coating is cured to prevent intermixing between the antireflective coating and the photoresist. The photoresist is exposed imagewise and developed. The antireflective coating in the exposed area is then typically dry etched using various etching gases, and the photoresist pattern is thus transferred to the substrate. In cases where the photoresist does not provide sufficient dry etch resistance, underlayers or antireflective coatings for the photoresist that act as a hard mask and are highly etch resistant during substrate etching are preferred, and one approach has been to incorporate silicon into a layer beneath the organic photoresist layer, either directly or below an additional organic coating, which maybe used to improve the lithography. A silicon layer directly beneath the photoresist layer is preferred. Silicon is highly etch resistant in processes where O2 etching is used, and by providing an organic mask layer with high carbon content beneath the silicon antireflective layer a very large aspect ratio can be obtained. Thus, the organic mask can be much thicker than the photoresist or silicon layer above it. The organic mask, which is much thicker, can provide the substrate etch masking that the original photoresist was incapable of. Furthermore, these silicon containing antireflective coatings that also reduce or eliminate the reflected exposure radiation are highly desirable.
The present invention provides for a novel antireflective coating composition for a photoresist, where the composition comprises novel silicon containing polymer capable of crosslinking, with or without the crosslinking catalyst. The invention also provides for a process for using the antireflective coating to form an image using the novel composition. In addition to being used as an antireflective coating composition, the novel composition may also be used as a hard mask for protecting the substrate from etching gases or may also be used as a low k dielectric material. The novel composition is useful for imaging photoresists which are coated over the novel antireflective coating composition and also for etching the substrate. The novel composition enables a good image transfer from the photoresist to the substrate, and also has good absorption characteristics to prevent reflective notching and line width variations or standing waves in the photoresist. Additionally, substantially no intermixing is present between the antireflective coating and the photoresist film. The antireflective coating also has good solution stability and forms thin films with good coating quality, the latter being particularly advantageous for lithography.